1. Field of the Invention
The present invention relates to a sequence controlling apparatus and more particularly to a sequence controlling apparatus for providing sequence outputs to a load apparatus, such as a solenoid and a motor, by making a logical operation of input signals from a sensor and the like.
2. Description of the Prior Art
As an old sequence controlling apparatus, a so-called relay sequencer has been known. In the relay sequencer, the wiring must be changed in order to change a program and thus it is difficult to obtain a general purpose sequencer.
Then, large-sized sequence controlling apparatus were utilized and used a large-sized computer to control a plant and the like. Although this type of sequence controlling apparatus using a large-sized computer overcomes a general purpose problem such as in an old sequencer, it is not suitable for a small-sized sequence controlling apparatus.
With advancement of a recent semiconductor technology, it is proposed that a small-sized central processing unit such as a microprocessor of microcomputer having a relatively complicated operation function may be utilized in a sequence controlling apparatus.
However, a sequence controlling apparatus using a microcomputer (central processing unit) is complex in the circuit structure and expensive and in addition to these, there is a problem of poor electrical noise-proofing. Furthermore, in case where a timer function is provided using a sequence controlling apparatus, the state of use of such timer function can not be seen from the outside and it is no easy to change the timer time, because in an apparatus using a central processing unit, the timer function is achieved by a program.